MEDICAL GEOLOGY IN GEOHAZARD/RISK ASSESSMENTS: THE EXAMPLE OF CO2 IN CAVES

Especially in Australia, Texas and Thailand, naturally elevated levels of CO2 in some karstic caves constitute a well-recognized geohazard. In addition, CO2 levels as high as 6% have been reported in three lava tube caves in Australia; an extraordinary biological community exists at that level. Further, many small, poorly ventilated cave chambers can serve as induced CO2 traps. Whether natural or human-induced, Appalachian and many other cavers and cave-oriented geoscientists and biologists are necessarily alert to clinically significant levels of CO2. These have been found to be readily detectible by changes in breathing. Worldwide, lethal CO2 levels exist mostly in karstic caves which are subject to volcanic emissions, e.g., thermal springs (temporary levels of 10% CO2 in some dissolutional Texas caves constitute a well-known exception). An empirically-determined maximum working level of 6% CO2 has been developed in Australia and unofficially adopted worldwide. Adequate knowledge of pulmonary physiology and its spelean applications is essential for accurate assessment of such hazards and risks. Certain recommendations of the National Commission on Risk Assessment and Risk Management also are highly pertinent. These include early and continued involvement of "stakeholders" in the assessment process, multidisciplinary search for relevant information, avoidance of both default decisions and command-and-control decisions, transdisciplinary peer review whenever time permits, and iterative management. Recent widely publicised hazard/risk assessments for a group of 200 well-ventilated, frequently visited caves ignored these principles. Instead they relied upon a temporary industrial elevation (to 8% CO2) in a nearby masonry-lined artificial subterranean instrument chamber plus speculative extrapolation of roadside CO2 measurements to volcanic caves several km away where no clinical symptoms of elevated CO2 have ever been observed. Resulting undesirable scientific, social and political impacts could easily have been avoided by proper application of medical geology.